diff --git a/src/proto.h b/src/proto.h
index 2471bb6..4c52d4b 100644
--- a/src/proto.h
+++ b/src/proto.h
@@ -146,6 +146,10 @@
 # include "version.pro"
 # include "window.pro"
 
+# ifdef FEAT_MZSCHEME
+#  include "if_mzsch.pro"
+# endif
+
 # ifdef FEAT_PYTHON
 #  include "if_python.pro"
 # endif